The present invention relates generally to cooling electric motors, and more particularly, to cooling high power, compact electric motors in aircraft.
Electric motors are used to drive a variety of mechanical components such as compressors, drive shaft components, and the like. In each application, electric power supplied to the motor creates heat. Generally, as the motor power increases, heat generated by the motor also increases. In some applications, the power density requires the motor to be actively cooled, for example, by air received by the component driven by the motor. Additionally, some applications utilize a cooling medium having physical properties that vary during operation. In some applications, physical property changes of the cooling medium can reduce the cooling efficiency of the electric motor.
In some aircraft, one or more cabin air compressors (CAC) are used to provide compressed air to a passenger cabin. Within cabin air compressors, an electric motor drives a radial compressor. Because of weight and physical constraints on the aircraft, the electric motor must be high power relative to its compact size. Thus, the power density of the electric motor requires cooling of the motor to maintain an acceptable motor temperature. Typically, the electric motor receives cooling air from the inlet duct of the compressor, which communicates with air exterior to the aircraft. As the aircraft increases altitude, the air density decreases. The lower air density causes decreased cooling efficiency and increased electric motor temperatures. Higher temperatures in the electric motor can lead to decreased motor life and/or premature electrical failure of the insulating materials contained within the motor. Thus, a need exists for improved cooling of electric motors, and specifically, for electric motors used in CAC of aircraft.